Optimizations introduced in
https://chromium-review.googlesource.com/c/v8/v8/+/1776079
are currently defeated since Address is not a pointer type.
Clang does not seem to carry over alignment information as range
information when casting to ints.
Using __builtin_assume we can restore the same effect. Additionally
we can help the compiler remember that when compressing the removed
bits are actually the cage base. This helps e.g. with
`decompress(compress(..))`.
See https://godbolt.org/z/5r68G5qa6 for details.
Bug: v8:9353
Change-Id: Ief016fce0788f2bef6b684a18b104ada6e6d3856
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4156060
Commit-Queue: Olivier Flückiger <olivf@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/main@{#85246}
77de44e1c4